The minimum intensity of light to be detected by human eye is 10- 10Wm- 2 . The number of photons of wavelength 5.6× 10- 7m entering the eye, with pupil area 10- 6m2 , per second for vision will be nearly

Question

The minimum intensity of light to be detected by human eye is 10- 10Wm- 2 . The number of photons of wavelength 5.6× 10- 7m entering the eye, with pupil area 10- 6m2 , per second for vision will be nearly (A) 100 (B) 200 (C) 300 (D) 400

Tardigrade Admin · Accepted Answer

Intensity of light is given as I=(P/A)=(n E/A) , where n is number of photons entering the eye, E is energy of each photon and A is area of pupil. n=(A I/E)=(A I λ /h c) , where λ is wavelength of photon. n=(10- 6 × 10- 10 × 5 × 10- 7/6 . 34 × 10- 34 × 3 × 108)=300 Hence, minimum 300 photons need to enter the eye of a person to detect light.

Q. The minimum intensity of light to be detected by human eye is $1 0^{- 10} W m^{- 2}$ . The number of photons of wavelength $5.6 \times 1 0^{- 7} m$ entering the eye, with pupil area $1 0^{- 6} m^{2}$ , per second for vision will be nearly

$100$

$200$

$300$

$400$

Q. The minimum intensity of light to be detected by human eye is 10−10Wm−2 . The number of photons of wavelength 5.6×10−7m entering the eye, with pupil area 10−6m2 , per second for vision will be nearly

100

200

300

400

Q. The minimum intensity of light to be detected by human eye is $1 0^{- 10} W m^{- 2}$ . The number of photons of wavelength $5.6 \times 1 0^{- 7} m$ entering the eye, with pupil area $1 0^{- 6} m^{2}$ , per second for vision will be nearly

$100$

$200$

$300$

$400$